Incandescent lamp



Jan. 27, 1942.

-K. '1. WADE 'INCANDESCENT LAMP Filed Jan. 17', 1940 Patented Jan. 27, 1942 UNITED STATES PATENT OFFICE INCANDE SCENT LAMP Kenneth L. Wade, New York, N. Y. Application January 17, 1940, Serial No. 314,227

2. Claims.

This application is a continuation-in-part of my Patent No. 2,191,189, issued February 20, 1940.

This invention primarily relates to improvements in an incandescent lamp and more particularly to improvements designed to make such a lamp more efficient and economical. The principal features of the improvements are embodied in the filament and in provisions for reflecting light rays and cleaning the gas currents inside an incandescent lamp of the vaporized particles of the filament which would otherwise soil the lamp globe.

Specifically this invention contemplates the fabrication and use of a filament having a grooved surface to reduce the losses from filament evaporation and to increase the eificiency of such a filament as much as possible by the use of grooves. Another contemplated improvement is the provision of a filter means to take out of the gas currents inside of a lamp the evaporated particles of the filament which are carried away by such currents and may be deposited on and stain the globe. Still another feature is a reflector so placed as to redirect those light rays from the filament which are originally headed towards the non-illuminating areas of the lamp. The desirability of these improvements immediately becomes apparent to those familiar with the problems of the art.

It has long been known that tungsten par- K ticles vaporized from the filament, causing a proportionate decrease in the size of the filament and normally also in the eificiency and life of the lamp. Further it was known that this action, While somewhat retarded by the surrounding gas in a gas-filled lamp, still took place in sufiicient measure to be the source of a brown deposit which adhered to the inside surface of the lamp globe. This deposit carried by convection currents inside such globe was chiefly objectionable from a light reducing viewpoint. A grooved filament may also be used in lamps such as electric discharge tubes where electron emission filaments perform with its concomitant advantages hereinafter set forth.

In a preferred embodiment, the new filament is grooved lengthwise at spaced intervals around its periphery. In cross section such a filament resembles a toothed gear in side elevation and by means of these grooves the normal evaporation loss of the filament is materially lessened. It may be that the sides of each groove produce this great advantage by blocking and retaining the particles vaporized from the opposing sides of the respective grooves, but the result achieved is a lamp filament having greater efiiciency and a longer life than the corresponding standard filament in use today. Similar benefits are obtained by using a filament of this type in any application of an incandescent filament, such as in the electron emission filaments of radio and X-ray tubes, where present day performance would be materially advanced by a reduction in evaporation loss of the filament.

In a similar fashion the grooves on the surface of the filament will produce areas of heat concentration where the heat rays are intercepted by the sides thereof.

Most lamps are gas-filled and the heating of such gas in proximity to the filament produces convection currents carrying away some portion of whatever particles are vaporized from the filament. These particles ofttimes are deposited on the globe in the illumination areas in the form of a brown deposit (for tungsten filaments) so that the positioning of a filter in the path of such currents to cut down the brown deposit is of considerable benefit. i True, the deposit would be made on the filter instead, which in one of the described forms is made of glass wool. Tungsten Wire and tungsten wool are other good filter materials particularly in connection with higher operating temperature lamps. The filters can be of the nest or screen variety. Since such a filter is placed in a position outside of the illumination zone, its effect would be very marked in keeping the currents and consequently the globe clean. As for the light rays which head towards the non-illuminating zone of the lamp, part of this invention is a mirror-like device which reflects such rays into the proper directions. Usually this device will be in the form of a small concave reflector placed adjacent the filament in the non-illumination region.

It is another object of this invention to retard the normal deposit of vaporized particles of a filament on the inside of the globe of such a lamp by the interposition of a filter in the path of flow of such particles.

It is still another object of this invention to reflect light rays which ordinarily fall in the nonilluminating zone of an incandescent lamp into the illuminating zone thereof.

Other objects, advantages and features will be had from a study of the balance of this specification and the accompanying drawing, in which:

Fig. 1 is a plan View of an incandescent lamp, partly in cross-section, showing one form of the filter of this invention for cleansing the convection currents of brown deposit;

Fig. 2 is a plan View of the filter assembled in Fig. 1;

Fig. 3 is similar to Fig. 1, but showing a modified form of such a filter;

Fig. 4 is a plan view of the filter assembled in Fig. 3.

Referring tothe drawing, in the incandescent lamp disclosed in Fig. 1, 2!] is the globe and 2| is the base thereof. Inside the lamp are filament 22 with the usual appurtenances and a filter 23. Filter 23 comprises an annular retainer 24 and the filter material 25. The lower portion IQ of the annular retainer 24shown in more detail in Fig. 2is concave and silvered so that it has a dual function being a reflector and partof a filter. The function of reflector portion I9 is the light rays originally directed toward the neck and base 2| of the lamp, comprising the. nonilluminating zone or region, are redirected toward that portion of globe 20 serving as alight passing surface or illumination area. The space between such .area and the filament 22 forms an illuminating zone for the purposes of this description. Naturally, the better the reflector the more light is redirected and'the-greater the saving. In assembling, reflector-retainer 24 is affixed in place over stem 25. Material 25 as shown, comprises glass wool or yarn or tungsten Wire or wool or other suitable material wound in fiat nest form around the stem 26 adjacent retainer 24 which serves to give it the needed stability. In operation .the filament heat sets up convection currents in ,the gas inside of globe 20. These currents, graphically indicated by arrows in Fig. 1, carry whatever vaporized tungsten particles escape from the filament 22 through suitable perforations 2 1 in retainer 24 and deposit suchparticles on the filter material 25. By these means the inside of globe 20 remains unsoiled because the gases coming in contact therewith have been previously cleaned by filter 23. The filter is always placed above the filament as shown in Fig. 1 with a base-up lamp. Even with a base-down lamp, a similar filter can be used although it would likely be smaller and closer to the filament. Another desirable form (not shown) would .be a conical spiral of filter material thread or wire surrounding stem 25 with the coil sufiiciently closely wound to intercept the currents carrying the vaporized particles of the filament.

The lamp of Fig. 3 comprises a globe 30 and a base 3|. The filament 32 is supported on a stem 33 and integral with said stem is a set of spiderlike arms 34 between which filter material 35 is wound. In operation the filter 36 operates precisely as does filter 25 (Fig. 1) but freer passage for convection currents is afforded by arms .34 than by reflector retainer 24 which is only perforated (Fig. 2). In assembling these filters the filter material in final position is squeezed .into'the lamp and afterwards any temporary disarrangement is corrected.

This .application is not limited by the theories expressed herein to explain the beneficial results obtained nor is the invention .of any narrower scopethan that defined by the following claims:

I claim:

1. In combination, in a gas filled incandescent lamp, an annular retainer member secured in substantially transverse relation to the stem of said lamp, and a separate filter of relatively large surface area retained by said retainer member, said retainer member having a light reflecting surface, said lamp having a gas circulation space on each side of said filter, a glass globe enclosing the above elements.

2. In combination, a gas filled incandescent lamp, a glass jglobe, an annular retainer member secured in substantially transverse relation to the stem ofsaid lamp, a separate filter of relatively large surface area retained by said retainer member, having a spaced clearance above and belowin said lamp globe whereby convection currents may pass from the clearance space on either side of the filter, through the filter, to the clearance space on .the opposite side of the filter.

KENNETH L. WADE. 

